Overview
ASTM E179-17(2022): Standard Guide for Selection of Geometric Conditions for Measurement of Reflection and Transmission Properties of Materials provides comprehensive guidance for selecting appropriate measurement geometries when evaluating the reflective and transmissive properties of materials. Developed by ASTM, this standard assists users in ensuring that optical appearance properties such as glossiness, opacity, lightness, transparency, and haziness are measured accurately and consistently using reflected or transmitted light. The guide emphasizes the importance of specifying geometric conditions because these influence measured values of appearance, even when color per se is not the attribute under direct evaluation.
Key Topics
- Geometric Measurement Scales: The guide covers critical terminology and measurement scales, distinguishing between regular (specular), diffuse, total, and directional reflection/transmission.
- Illumination and Viewing Angles: Accurate specification and selection of incident and viewing angles, azimuthal and rotation angles, and aperture sizes for different instruments.
- Specimen Preparation: Recommendations for specimen flatness, thickness, surface quality, and environmental conditioning to ensure representative results.
- Types of Reflection and Transmission: Comprehensive descriptions of how to measure and report regular and diffuse reflection/transmission, gloss, haze, and related appearance attributes.
- Instrumentation Considerations: Guidance on instrument setup to minimize vignetting and ensure compliance with the Helmholtz reciprocal relation for reliable, reproducible measurements.
- Applicability: Practical directions for diverse materials including opaque, translucent, and transparent substrates in forms ranging from liquids to coated surfaces.
Applications
The methodologies in ASTM E179-17(2022) are used widely in research, product development, manufacturing, and quality assurance where understanding and communicating optical appearance is essential. Common applications include:
- Material Quality Control: Ensuring consistency in the gloss, transparency, or opacity of manufactured products such as ceramics, plastics, coatings, textiles, and glass.
- Product Development: Selecting appropriate appearance attributes for new materials and comparing prototypes with reference standards.
- Process Optimization: Adjusting formulation or processing parameters in response to measured differences in reflection or transmission properties.
- Regulatory Compliance and Specification: Preparing documentation to meet international trade requirements and technical barriers to trade (TBT) as outlined by the WTO, supported by globally recognized terminology and practices.
- Comparative Analysis: Resolving discrepancies in appearance measurements among multiple measurement geometries or across different sites and instruments.
By clarifying geometric measurement conditions, this standard supports precise communication across supply chains and facilitates the resolution of technical disputes regarding appearance measurements.
Related Standards
Several ASTM and CIE standards are referenced for implementation alongside ASTM E179-17(2022), including but not limited to:
- ASTM D523: Test Method for Specular Gloss
- ASTM E1331: Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical Geometry
- ASTM D1003: Test Method for Haze and Luminous Transmittance of Transparent Plastics
- ASTM E1164: Practice for Obtaining Spectrometric Data for Object-Color Evaluation
- ASTM E2194 and E2539: Test Methods for Multiangle Color Measurement of Gonioapparent Materials
- CIE Publication No. 15: Colorimetry
- CIE Publication No. 17: International Lighting Vocabulary
These related standards offer detailed protocols for specific test scenarios and materials. By adhering to ASTM E179-17(2022) in conjunction with these references, organizations can ensure robust, standardized, and internationally accepted characterization of appearance properties.
Keywords: geometric conditions, reflection measurement, transmission measurement, gloss measurement, opacity, transparency, ASTM E179, appearance properties, optical properties, material standards.